The present invention relates generally to an electrical penetration assembly and, more particularly, to a containment electrical penetrator for conducting electrical current from points outside a thick reactor containment wall to points within the containment wall without allowing leakage of gas or fluids through the containment wall.
The rapidly expanding demand for increased electrical energy in a pollution-free atmosphere has required an increase in the construction of nuclear power generating plants. These plants are designed and constructed to anticipate the most severe of nature's adversities. The nuclear power generating plant is built with a thick reactor containment wall, typically five feet thick, such that it is necessary to provide electrical connections from points outside the wall to points within the wall without allowing leakage of gas or fluids through the wall. These electrical connections are for instrumentation, control, and power functions and also include rod position, radiation monitoring, and temperature instrumentation and control as well as power for fuel transfer cooling pumps, valves and recirculating fans.
Normally, the penetration assembly comprises a canister which is mounted within the containment wall and has a number of copper conductors extending therethrough for making electrical connections. To allow for thermal expansion differences between the canister and the copper conductors, copper rod-to-cable crimp or solder joints or sliding pin-socket joints have been necessary within the canister. Joints such as these degrade the electrical current carrying capacity of the penetration assembly, can result in excess heat and may not have the structural strength required to withstand extreme mechanical forces which result during short circuit conditions. Also, normally the conductors are a permanent non-repairable part of the penetration assembly, by virtue of being sealed in the canister end plates with epoxy, glass or ceramic. The canister is normally welded into the containment wall and should a defect occur in any one conductor, the entire penetration must be cut out and replaced, resulting in great expense because of both the cost of the penetration assembly and the length of time required for reactor shut-down. Also, penetration assemblies must be installed from both the outboard and inboard sides of the containment wall which results in the installer working inside the wall for a significant length of time where he is exposed to reactor radiation.
The purpose of the present invention is to overcome the attendant disadvantages of the presently used electrical penetration assemblies by providing an assembly in which the conductors have greater current carrying capacity and greater conductivity, thereby minimizing overheating problems. Also, another purpose of the invention is to provide an electrical penetration assembly in which any individual conductor within the canister may be removed with a minimum of cost and down-time, thus avoiding the necessity of cutting out the entire penetration canister from the containment wall. Further, it is an object of the invention to provide a penetration assembly in which the conductors therein may be replaced from outside the containment wall.